Messages in this thread Patch in this message | | | From | Avi Kivity <> | Subject | [PATCH][RFC] pte notifiers -- support for external page tables | Date | Wed, 5 Sep 2007 22:32:44 +0300 |
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[resend due to bad alias expansion resulting in some recipients being bogus]
Some hardware and software systems maintain page tables outside the normal Linux page tables, which reference userspace memory. This includes Infiniband, other RDMA-capable devices, and kvm (with a pending patch).
Because these systems maintain external page tables (and external tlbs), Linux cannot demand page this memory and it must be locked. For kvm at least, this is a significant reduction in functionality.
This sample patch adds a new mechanism, pte notifiers, that allows drivers to register an interest in a changes to ptes. Whenever Linux changes a pte, it will call a notifier to allow the driver to adjust the external page table and flush its tlb.
Note that only one notifier is implemented, ->clear(), but others should be similar.
pte notifiers are different from paravirt_ops: they extend the normal page tables rather than replace them; and they provide high-level information such as the vma and the virtual address for the driver to use.
Signed-off-by: Avi Kivity <avi@qumranet.com>
diff --git a/include/linux/mm.h b/include/linux/mm.h index 655094d..5d2bbee 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -14,6 +14,7 @@ #include <linux/debug_locks.h> #include <linux/backing-dev.h> #include <linux/mm_types.h> +#include <linux/pte_notifier.h> struct mempolicy; struct anon_vma; @@ -108,6 +109,9 @@ struct vm_area_struct { #ifndef CONFIG_MMU atomic_t vm_usage; /* refcount (VMAs shared if !MMU) */ #endif +#ifdef CONFIG_PTE_NOTIFIERS + struct list_head pte_notifier_list; +#endif #ifdef CONFIG_NUMA struct mempolicy *vm_policy; /* NUMA policy for the VMA */ #endif diff --git a/include/linux/pte_notifier.h b/include/linux/pte_notifier.h new file mode 100644 index 0000000..d28832b --- /dev/null +++ b/include/linux/pte_notifier.h @@ -0,0 +1,52 @@ +#ifndef _LINUX_PTE_NOTIFIER_H +#define _LINUX_PTE_NOTIFIER_H + +#include <linux/list.h> + +struct vm_area_struct; + +#ifdef CONFIG_PTE_NOTIFIERS + +struct pte_notifier; + +struct pte_notifier_ops { + void (*close)(struct pte_notifier *pn, struct vm_area_struct *vma); + void (*clear)(struct pte_notifier *pn, struct vm_area_struct *vma, + unsigned long address); +}; + +struct pte_notifier { + struct list_head link; + const struct pte_notifier_ops *ops; +}; + + +void vma_init_pte_notifiers(struct vm_area_struct *vma); +void vma_close_pte_notifiers(struct vm_area_struct *vma); +void pte_notifier_register(struct pte_notifier *pn, + struct vm_area_struct *vma); +void pte_notifier_unregister(struct pte_notifier *pn); + +#define pte_notifier_call(vma, function, args...) \ + do { \ + struct pte_notifier *__pn; \ + \ + list_for_each_entry(__pn, &vma->pte_notifier_list, link) \ + __pn->ops->function(__pn, vma, args); \ + } while (0) + +#else + +static inline void vma_init_pte_notifiers(struct vm_area_struct *vma) {} +static inline void vma_close_pte_notifiers(struct vm_area_struct *vma) {} +static inline void pte_notifier_register(struct pte_notifier *pn, + struct vm_area_struct *vma) {} +static inline void pte_notifier_unregister(struct pte_notifier *pn) {} + +#define pte_notifier_call(vma, function, args...) \ + do { } while (0) + +#endif + + +#endif diff --git a/mm/Kconfig b/mm/Kconfig index e24d348..7b10151 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -176,3 +176,6 @@ config NR_QUICK config VIRT_TO_BUS def_bool y depends on !ARCH_NO_VIRT_TO_BUS + +config PTE_NOTIFIERS + bool diff --git a/mm/Makefile b/mm/Makefile index 245e33a..59f6a03 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -29,4 +29,5 @@ obj-$(CONFIG_FS_XIP) += filemap_xip.o obj-$(CONFIG_MIGRATION) += migrate.o obj-$(CONFIG_SMP) += allocpercpu.o obj-$(CONFIG_QUICKLIST) += quicklist.o +obj-$(CONFIG_PTE_NOTIFIERS) += pte_notifiers.o diff --git a/mm/mmap.c b/mm/mmap.c index b653721..cc6c4fe 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1134,6 +1134,7 @@ munmap_back: vma->vm_page_prot = protection_map[vm_flags & (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]; vma->vm_pgoff = pgoff; + vma_init_pte_notifiers(vma); if (file) { error = -EINVAL; diff --git a/mm/pte_notifier.c b/mm/pte_notifier.c new file mode 100644 index 0000000..0b9076c --- /dev/null +++ b/mm/pte_notifier.c @@ -0,0 +1,32 @@ + +#include <linux/pte_notifier.h> + +void vma_init_pte_notifiers(struct vm_area_struct *vma) +{ + INIT_LIST_HEAD(&vma->pte_notifier_list); +} +EXPORT_SYMBOL_GPL(vma_init_pte_notifiers); + +void vma_destroy_pte_notifiers(struct vm_area_struct *vma) +{ + struct pte_notifier *pn; + struct list_head *n; + + list_for_each_entry_safe(pn, n, &vma->pte_notifier_list, link) { + pn->ops->close(__pn, vma); + __list_del(n); + } +} + +void pte_notifier_register(struct pte_notifier *pn, struct vm_area_struct *vma) +{ + list_add(&pn->link, &vma->pte_notifier_list); +} +EXPORT_SYMBOL_GPL(pte_notifier_register); + +void pte_notifier_unregister(struct pte_notifier *pn) +{ + list_del(&pn->link); +} +EXPORT_SYMBOL_GPL(pte_notifier_unregister); + diff --git a/mm/rmap.c b/mm/rmap.c index 41ac397..3f61d38 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -682,6 +682,7 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, } /* Nuke the page table entry. */ + pte_notifier_call(vma, clear, address); flush_cache_page(vma, address, page_to_pfn(page)); pteval = ptep_clear_flush(vma, address, pte); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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